Research Initiative Treatment Action (RITA!); January 24, 2000
 

GlaxoWellcome Inc. has just released a revised product warning for its drug, abacavir sulfate (Ziagen). This nucleoside analogue reverse transcriptase inhibitor is used with other antiretrovirals for the treatment of HIV-1 infection. The revised warning emphasizes the potential importance of respiratory symptoms during the presentation of hypersensitivity reactions in patients taking abacavir. Hypersensitivity frequently includes fever, rash, nausea, gastrointestinal symptoms (nausea, vomiting, diarrhea or abdominal pain) and fatigue or malaise.

A recent review of cases revealed that respiratory symptoms including cough, dyspnea (shortness of breath), and pharyngitis (sore throat) occurred in approximately 20% of patients having hypersensitivity reactions. Deaths have been reported in patients receiving abacavir who were initially diagnosed with an acute respiratory disease, but were later recognized to have had hypersensitivity reactions. If respiratory symptoms such as cough, dyspnea, and/or pharyngitis occur with other symptoms associated with hypersensitivity, the patient must immediately and permanently stop taking abacavir. Continuation or re-introduction of abacavir can lead to more severe symptoms within hours, and may include life-threatening hypotension and death.

Hypersensitivity is manifest in multi-organ system involvement. Respiratory symptoms alone do not justify a diagnosis of hypersensitivity. Also, respiratory symptoms such as runny nose or wheezing are not commonly considered respiratory symptoms associated with hypersensitivity. However, if the clinical presentation of an acute respiratory illness cannot be clearly distinguished from a hypersensitivity reaction, abacavir must be permanently discontinued. Once abacavir is discontinued, hypersensitivity symptoms should resolve quickly.

Current data are insufficient to indicate that age, gender, ethnicity, previous respiratory conditions, smoking or side effects from other drugs influence the predisposition to or outcome of hypersensitivity to abacavir. Although some laboratory indicators such as decreased lymphocyte and platelet counts may indicate a hypersensitivity reaction, physicians should rely on the clinical presentation of abacavir hypersensitivity in establishing a diagnosis. Information from chest X-rays may be unclear and does not enable a clear diagnosis of respiratory symptoms associated with abacavir hypersensitivity.

GlaxoWellcome is planning a prospective clinical study to examine these matters further. The company requests that all cases of hypersensitivity reaction occurring in patients treated with abacavir be reported to the Abacavir Hypersensitivity Reaction Registry at GlaxoWellcome (1.800.270.0425) or to the FDA MedWatch program (1.800.FDA.1088). Any questions from health care professionals can be directed to the GlaxoWellcome Drug Information Department (1.800.334.0089).

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Abacwarn

Copyright © 1999 - Research Initiative Treatment Action (RITA!). Reproduced with permission. RITA! is published by The Center for AIDS. Contact Thomas Gegeny, MS, ELS, Editor, RITA! for permission to reproduce RITA!. tom@centerforaids.org. http://www.centerforaids.org